Great forsight! Even a minute of taking your eyes off a child could result in tragedy. im glad you and your wife were thinking ahead.4 year old and 6 months. I think if it was just the 4 year old, I wouldn't be too concerned but I have a feeling our smaller one is going to be her own boss and just go where she wants.
You're right, it effectively sits like a table. It has legs that I've cut to length based on the depth at that point. I'll just lift it out when I don't need it any more.
My hubby and I were renting a house once, and had no idea that behind a big bush was a hole in the fence our 3 yr old could fit through. Well, guess what, we had to scour the neighborhood for him, he disappeared that quick...just cuz we thought we were safe in our own back yard.